An alternative procedure in the tetrazolium test for soybean seed

O objetivo deste estudo foi desenvolver um procedimento alternativo para redução do período de precondicionamento de sementes de soja no teste de tetrazólio. Foram empregados dois tamanhos de sementes de doze cultivares de soja [Glycine max (L.) Merrill], produzidas em Londrina, PR, em 1993 e 1994. Os tratamentos utilizados foram dois períodos de embebição (quatro horas e seis horas) na temperatura de 41oC, tendo como testemunha o procedimento-padrão de dezesseis horas, a 25oC. Os parâmetros usados para avaliar os tratamentos foram o vigor [TZ (1-3)], a viabilidade [TZ (1-5)], a deterioração por umidade [TZ (6-8)], o dano mecânico [TZ (6-8)], as lesões por percevejos [TZ (6-8)] e o teor de água das sementes. O período de seis horas a 41oC propiciou condições adequadas de coloração das sementes, o que permitiu a avaliação e interpretação do vigor, da viabilidade, da deterioração por umidade, do dano mecânico e das lesões por percevejos. Usando-se seis horas de precondicionamento a 41oC, há uma redução de dez horas na execução do teste, em comparação ao procedimento atualmente recomendado, sem compremeter a precisão requerida.The aim of this work was to develop an alternative procedure for reducing the soybean seed preconditioning in the tetrazolium test. Two imbibition periods (four and six hours) at 41oC were tested and compared to the traditionally recommended period for preconditioning of 16 hours at 25 ºC. Seeds of twelve cultivars were used, and classified into two sizes. The parameters used were: vigor [TZ (1-3)]; viability [TZ (1-5)]; weathering [TZ (6-8)]; mechanical damage [TZ (6-8)]; stink bug damage [TZ (6-8)]; and seed moisture content. The staining pattern developed on the seeds after a preconditioning period of six hours at 41 ºC is suitable for the evaluation of the quality of soybean seeds by the tetrazolium test. Seed preconditioning procedures for the tetrazolium test evaluated in this experiment were not affected by the size of soybean seeds; the 6 hour/41oC treatment reduces the period of preconditioning by ten hours when compared to the recommended procedures of 16 hours at 25ºC. To sum up, in the tetrazolium test for soybean seeds, the preconditioning conditions of 6 hour/41oC can be used successfully, without impairing the precision required by the test

Standardization of the accelerated aging test for evaluation of wheat seed vigor

Abstract: The accelerated aging test is widely used to evaluate seed vigor. However, for the wheat crop, discrepancies are found in the literature regarding temperature and period of exposure to stress. This study aimed to evaluate the efficiency of the accelerated aging test in different combinations of time and temperature in seed vigor evaluation in wheat lots and cultivars. The following cultivars were used: Tbio Sintania, Tbio Sossego, Tbio Sinuelo, LG Oro, Tbio Toruk, and CD 150 (Group 1), represented by one lot each, and five lots of the cultivar CD 150 (Group 2). Water content, germination, first count of germination, and seedling emergence in the field were evaluated for characterization of initial physiological potential. Then the accelerated aging test was applied to the lots under the following aging conditions: 41 °C / 48 and 72 h, 43 °C / 40 and 48 h, and 45 °C / 24 and 40 h in plastic boxes, with 40 mL of distilled water and seeds distributed in a single layer on a screen. After aging, the water content and germination of the seeds were determined. Analysis of variance was performed on the data, and the means were compared by Tukey’s test, at 5% probability. The simple correlation test (r) was performed between the analyzed variables and the seedling emergence in the field test. The accelerated aging test with the combinations of 41 °C / 72 h and 43 °C / 48 h is efficient for evaluating seed vigor of wheat lots and cultivars. The combination of 43 °C / 48 h provides results more quickly, saving 24 h in relation to the methodology recommended in the literature (41 °C / 72 h)

Tetrazolium test adjustment for wheat seeds

The assessment of the germination test in wheat seeds varies from 4 to 15 days, because the species normally presents dormancy in freshly harvested seeds. The tetrazolium test can characterize seed viability in less than 24 hours including lots with dormancy seeds. The objective of this study was to develop a practical and efficient procedure for evaluating the viability of wheat seeds using the tetrazolium test. Five seed lots of the BRS 208 cultivar were used, where the following were tested: a) pre-conditioning between moist paper towels or direct immersion in water for 18 hours, at 20 °C; b) longitudinal section of the embryo and the endosperm; c) coloration on paper or by immersion for 2 and 3 hours, at 30 and 40 °C; and d) concentrations of tetrazolium solution at 0.075%, 0.1%, 0.5% and 1.0%. The tetrazolium test may be efficiently used to evaluate wheat seed viability by pre-conditioning the seeds between paper towels (18 hours, at 20 °C) and adopting the following combinations of preparation and coloration: coloration of both halves of the seed on paper (2 hours, at 30 °C), in a 1.0% tetrazolium solution; or coloration of one half of the seed by immersion (3 hours, at 30 °C), in a 0.1% tetrazolium solution; or coloration of one half of the seed by immersion (2 hours, at 40 °C), in a 0.075% tetrazolium solution. This latter procedure is recommended for identifying and discarding lots with lower viability

Effects of phosphine fumigation on the quality of soybean seeds

Fumigation is a technique employed to eliminate insect pests in stored seeds by using gas. The aim of the experiment was to evaluate the effect of the gas phosphine on germination and on vigor (accelerated aging and seedling length) of soybean seeds. Soybean seeds of two cultivars with two vigor levels were used. Each treatment was replicated four times and each experimental unit consisted of two kilograms of seeds, which were placed in individual 1 m³ gas-tight capacity chambers with phosphine. The concentrations used were 1.0; 2.0 and 3.0 g PH3.m-3, achieved by applying 3.0; 6.0 and 9.0 g of Fertox® commercial formulation. During seven days, the phosphine gas concentration within each chamber was monitored using the Silochek® gas meter. After this period, the chambers were opened, the seeds were removed and the quality analyses were performed. Throughout the experiment, PH3 concentrations in the chambers remained at the concentrations required for the elimination of all life stages of insect pests of stored seed. Even in the lowest dosage, the gas concentration remained above 400 ppm that is considered the minimum concentration for eliminating insect pests. No detrimental effects were detected on the physiological quality of the fumigated seeds

Análise estrutural de vagens e sementes de soja submetidas à deterioração por umidade em pré-colheita

The objective of this work was to analyze structurally the pods and seed coats of soybean (Glycine max) cultivars, as well as to determine the quality of seeds when subjected to deterioration by weathering in pre-harvest. A 7×3 factorial arrangement was used – seven cultivars and three volumes of simulated rainfall (0, 54, and 162 mm). Exposure to rainfall was simulated in the R8 phenological stage. Then, the plants were taken to a greenhouse, where they were kept until the time of collection of pods and seeds. After collection, the following evaluations were carried out: tetrazolium test, lignin content in pods and seed coats, and structural analysis of pods (exocarp, mesocarp, and endocarp thickness) and seed coats (epidermis, hypodermis, and parenchymal-cell thickness). Pre-harvest rainfall of 54 and 162 mm reduces the quality of soybean seeds; however, the response to deterioration by weathering differs according to the cultivar. The tolerance to all simulated rainfall was greater for BRSMT Pintado, BRS Jiripoca, and M8210IPRO and lower for BRS 1010IPRO. Pods with a greater thickness of the exocarp, mesocarp, and endocarp and a high lignin content show greater resistance to weathering deterioration and seeds with greater vigor and viability. The thickness of the hypodermis of the testa is related to resistance to weathering deterioration and to the obtainment of high-quality seeds.O objetivo deste trabalho foi analisar estruturalmente as vagens e os tegumentos de cultivares de soja (Glycine max), bem com determinar a qualidade das sementes quando submetidas à deterioração por umidade em pré-colheita. Utilizou-se arranjo fatorial 7×3 – sete cultivares e três volumes de precipitações pluviais simuladas (0, 54 e 162 mm). A exposição à chuva foi simulada no estádio fenológico R8. Em seguida, as plantas foram levadas à casa de vegetação, onde foram mantidas até a coleta das vagens e das sementes. Após a coleta, realizaram-se as seguintes avaliações: teste de tetrazólio, teor de lignina nas vagens e nos tegumentos, e análise estrutural de vagens (espessura do exocarpo, do mesocarpo e do endocarpo) e tegumentos (espessura da epiderme, da hipoderme e das células parenquimatosas). Precipitações de 54 e 162 mm em pré-colheita reduzem a qualidade das sementes de soja; entretanto, a resposta à deterioração por umidade difere de acordo com a cultivar. A tolerância a todas as precipitações pluviais simuladas foi maior para BRSMT Pintado, BRS Jiripoca e M8210IPRO e menor para BRS 1010IPRO. Vagens com maior espessura do exocarpo, do mesocarpo e do endocarpo e elevados teores de lignina apresentam maior tolerância à deterioração por umidade e sementes com maior vigor e viabilidade. A espessura da hipoderme da testa de tegumentos está relacionada à tolerância à deterioração por umidade e à obtenção de sementes de elevada qualidade

Soybean seed moisture content and methods of evaluating the mechanical damage in the pendulum test

Sementes de doze cultivares de soja (Glycine max (L.) Merrill), colhidas em maturação fisiológica (R7), trilhadas manualmente e condicionadas para os teores de umidades de 9%, 11% e 13%, foram submetidas ao impacto do pêndulo, correspondente à energia cinética de 0,3185 joule. Nas avaliações dos danos, foram utilizados dois métodos. No método de tetrazólio, foi usado um sistema de notas para quantificar o dano mecânico, e no método de hipoclorito de sódio, foi considerado o número de sementes intactas não intumescidas pela solução. Os dois métodos foram sensíveis para distinguir as classes de resistência entre os genótipos testados nos três teores de umidade. O teor de umidade de 13% permitiu a melhor classificação das doze cultivares quanto à resis-tência da semente ao dano mecânico provocado pelo impacto do pêndulo nos dois métodos de ava-liação (r = 0,95). Os resultados comprovam a possibilidade da utilização do teste de hipoclorito de sódio como alternativa (mais expedito e menos oneroso) ao teste de tetrazólio no teste do pêndulo, para seleção de genótipos de soja com semente resistente ao dano mecânico.Twelve soybean cultivars (Glycine max (L.) Merrill) were harvested and hand-threshed at R7 and conditioned to 9%, 11% and 13%, moisture content before to be stressed in the pendulum test, that applied a kinetic energy of 0.3185 joule on the seed. In the evaluation system of tetrazolium test a grade score was adopted to quantify the results, and for the sodium hypochlorite test the number of swelled seeds was used. Both methods prove to be accurated to identify the levels of resistance among the genotypes tested. The 13% moisture content allowed the best screening related to the mechanical damage resistance under the pendulum test, in the two evaluation methods (r = 0.95). The results confirm the possibility of utilizing the sodium hypochlorite tests as an alternative of low cost and easy made for the tetrazolium test, in the process of soybean genotype selection for the mechanical damage resistance under the pendulum test

Lignin monomeric composition in soybean seed coats and resistance to mechanical damage

Abstract: Soybean seeds are crucial for global food production. Various factors affect the quality of soybean seeds, including mechanical damage, which can lead to reduced germination potential and decreased seedling vigor. The presence of lignin in the seed coat contributes to resistance to mechanical damage. However, the relationship between the monomeric composition of lignin and mechanical damage is unknown. To fill this gap, we evaluated the contents of monomers hydroxyphenyl (H), guaiacyl (G), and syringyl (S) in seed coats of three cultivars of soybean, namely, Doko, IAS-5, and Savana. The results revealed that the monomeric composition of lignin varied between resistant and susceptible cultivars. The levels of G and S monomers were inverse in the cultivars Doko and Savana, suggesting that the composition of lignin monomers may play a crucial role in the resistance of soybean seeds to mechanical damage. In addition, negative linear regressions between lignin and S monomer contents and S/G ratios could be helpful as an alternative to identify resistance in soybean seeds